The present invention relates to a buffer circuit and, more particularly, to an n-channel open drain or a p-channel open drain buffer circuit.
An open drain buffer circuit of the type described is extensively used today. A conventional n-channel open drain buffer circuit is implemented as an n-channel MOS transistor having a gate electrode connected to an input terminal, a drain electrode connected to an output terminal, and a source electrode connected to ground. On the other hand, a conventional p-channel open drain buffer circuit is constituted by a p-channel MOS transistor having a gate electrode connected to an input terminal, a drain electrode connected to an output terminal, and a source electrode connected to a power source. Such conventional open drain buffer circuits have problems left unsolved, as follows. Assume that a single signal line is shared by a plurality of devices on a time division basis, and that the devices are implemented by the conventional open drain buffer circuits. Then, the n-channel open drain buffer circuit would slow down the rise of the signal while the p-channel drain buffer circuit would slow down the fall of the signal.